MOVEMENT 6i 



the musical note in unison therewith. Thus it has been 

 found that a Common White Butterfly (Pieris) makes only 

 nine wing-strokes a second as contrasted with the 190 

 strokes a second of the Hive-bee (Apis), or the 330 strokes 

 a second of a Housefly (Musca). 



Relatively large insects with extensive wing- area and 

 powers of prolonged, often soaring flight, have a rate of wing- 

 motion intermediate between these extremes. A dragonfly, 

 for example, may beat its wings twenty-eight times a second 

 as it hawks through the air in pursuit of its prey. The 

 different instances mentioned may serve to illustrate how, 

 in every case, the special features of an insect's flight corre- 

 spond with its peculiar way of life. Further consideration 

 of flight in relation to the general behaviour and environment 

 of insects may be deferred till a later chapter. 



Walking, running, leaping, crawling, and flying are 

 obvious modes of movement which cannot be overlooked 

 by the most casual observer of insects. But there are many 

 other movements of equal importance to the creature's life, 

 which, though less conspicuous, are all brought about by 

 muscular action. An insect continually moves its feelers 

 as though seeking to test the neighbourhood into which it 

 advances ; these movements are due to the contraction of 

 small muscles passing from the inside of the head-capsule 

 to the feeler's basal segments. The feelers are, as already 

 stated, modified Hmbs in series with the insect's legs. The 

 three pairs of jaws (mandibles, maxillae, and labium) whose 

 position and action were briefly described in the last chapter 

 (pp. 17-23) in relation to the function of feeding, are 

 likewise modified limbs. The muscles by which these 

 jaws are worked are often numerous and always, in view 

 of their use in nutrition, important. Some description of 

 their arrangement may therefore be given first in a biting 

 and then in a sucking insect. 



The jaws and their muscles in the cockroach, a typical 

 biting insect, have been described in detail by J. Mangan 

 (1908). The Cockroach's mandible with its apical teeth 

 and molar area, its convex and concave articulations (condyle 



